Multiple electrode flashlamp circuit with a gas holdoff tube in circuit with a trigger electrode adjacent the anode



Nov. 8, 1966 J. H. GONCZ MULTIPLE ELECTRODE FLASHLAMP CIRCUIT WITH A GAS HOLDOFF TUBE IN CIRCUIT WITH A TRIGGER ELECTRODE ADJACENT THE ANODE Filed Jan. 29, 1964 TRIGGER SOURCE JOHN H. GONCZ I NVENTOR.

wi mfwwg ATTORNEYS Unite States Patent H MULTKPLE ELECTRUDE FLASHLAMP CIRCUIT WITH A GAS HULDUFF TUBE 1N CHRCUET WITH A TRIGGER ELECTRUDE ADJACENT THE ANODE John H. Goncz, Waltham, Mass, assignor to Edgerton,

Gerrneshausen & Grier, llnc., Boston, Mass, a corporation of Massachusetts Filed .lan. 29, 1964, Ser. No. 341,060 5 Claims. (Cl. 315-168) This invention relates to electric systems for controlling the operation of electric discharge devices, and more particularly to such systems in which the discharge device has a plurality of trigger electrodes disposed in the discharge path between the principal electrodes.

In such devices, the discharge arc is extended over a considerable distance through the use of multiple trigger electrodes. This feature, although advantageous for many reasons, is not without problems. Among these problems are the relatively long commutation delay time, and jitter in the discharge arc. Commutation delay time is the time which elapses between the application of the triggering impulse and the formation of the discharge are within the device. litter is the time difference observed in commutation delay times when the device is triggered at high repetition rates.

It is, therefore, an object of this invention to provide a new and novel electric system for controlling the operation of discharge devices with multiple trigger electrodes.

Another object of this invention is to provide an electric circuit that greatly reduces commutation delay time.

A further object is to provide a positive triggering system to reduce or eliminate jitter.

In summary, my invention utilizes a breakdown device in the circuitry of the trigger electrode adjacent the highvoltage principal electrode to hold the trigger pulse off that trigger electrode until it builds up to a substantially higher potential than that on the other trigger electrodes. The breakdown device then passes this pulse thereby insuring that this trigger electrode is the last to fire and does so with a more intense triggering pulse.

Other and further objects will be hereinafter pointed out in the following specification and more particularly in the appended claims.

My invention will be better understood by referring to the following description taken in conjunction with the attached drawing, the single figure of which is a schematic drawing of the preferred embodiment of my invention.

Referring now to the circuit shown in the drawing, an electric device is shown having a pair or" principal electrodes 2i) and 30 with a plurality of trigger electrodes 11, 12, 13, 14 and disposed therebetween. The discharge device 119 may be of the type disclosed in U.S. Letters Patent No. 2,977,508, issued on March 28, 1961 to Kenneth I. Germeshausen, entitled Gaseous-Discharge Device and System, and assigned to the same assignee as the present invention, or any other similar device in which the principal electrodes are separated by a considerable distance and a plurality of probe-type trigger electrodes are disposed in the space therebetween to aid in ionizing the discharge path and guiding the discharge arc.

Connected across the principal electrodes and 31 is a source of high voltage potential represented as a capacitor 21 which may be charged from a power supply (not shown) through terminals 31 and 33. Capacitor 21 applies a high voltage potential across principal electrodes 20 and 39 which potential is normally ineffective in producing a discharge arc between the principal electrodes. When, however, triggering impulses are applied to the trigger electrodes 11, 12, 13, 14 and 15 and the discharge path is ionized, this potential is effective to cause a sudden,

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high-energy discharge between the principal electrodes Ztl and 30.

A source of triggering impulses 24 is provided to energize the trigger electrodes 11, 12, 13, 14 and 15 to permit a discharge to take place within device 10. The source 24 may be a trigger circuit of the type taught in US Letters Patent No. 2,478,901 issued on August 16, 1949 to Harold E. Edgerton, and entitled Electric System, and assigned to the same assignee as the present invention or any other source of high-voltage pulses. A step-up trigger pulse transformer 26 may be used to increase the voltage or" the triggering impulses from trigger source 24. Primary winding 28 is connected to the source of trigger ing impulses 24 while the secondary winding 27 is connected to trigger electrode 11 through breakdown device 25 and to each of trigger electrodes 12, 13, 14 and 15 via common point 29. From this common point 2%, the trigger pulse is fed to trigger electrodes 12, 13, 14 and 15 through isolating impedances such as, for example, isolating capacitors 16, 17, 18 and 19 respectively. Isolating impedances are employed to insure that the triggering impulse is applied individually to each of the trigger elec* trodes, and that each trigger electrode individually discharges its potential.

Trigger electrode 11 is connected to secondary winding 27 of transformer 26 through breakdown device 25 for reasons hereinafter set forth. Breakdown device 25 may be any electric or electronic component that has the characteristic of holding oil? voltage pulses until such time as they reach a predetermined voltage level at which time, they instantly become conductive and pass the pulse as a spike or burst of energy. Diodes may be used as the breakdown device, including gas-filled, vacuum, semiconductor or solid-state diodes as long as they (1) hold off pulses up to a predetermined voltage and (2) pass the pulse very rapidly once the predetermined voltage is reached. Spark gaps work very well as the breakdown device 25 and our best results have been obtained using a spark gap of the type disclosed in the copending application for 113. Letters Patent Serial No. 292,867, filed July 5, 1965 by Louis Lucas, entitled Electric-Discharge Device," and assigned to the assignee hereof. Breakdown device 25 may be disposed within the envelope of device 10, but preferably, it is disposed outside the device where it can be adjusted or replaced as may be necessary.

In operation, capacitor 21 is charged to a high voltage potential from a power supply (not shown) through terminals 31 and 33. This otential is maintained across the principal electrodes 20 and 30. When it is desired to discharge this energy within device 10, a trigger pulse is fed from the source of triggering impulses 24 to the primary winding 28 of step-up trigger transformer 26 where it induces a high voltage trigger pulse in the secondary winding 27. This trigger pulse is fed substantially simultaneously to breakdown device 25 and to each of trigger electrodes 12, 13, 14 and 15 through isolating impedances 16, 17, 18 and 19 respectively.

Let us consider principal electrode Ztl as the high-voltage or anode electrode and principal electrode 3!) as the lowvoltage or cathode electrode. When the high-voltage trigger pulse from the secondary winding 27 is present at the end of trigger electrode 15, it causes the medium thereabout to become ionized and a discharge to pass from trigger electrode 15 to cathode 31 As a result of this discharge, the potential on trigger electrode 15 drops to substantially cathode or ground potential. The greatest voltage gradient is now present between trigger electrode 14 with its high-voltage trigger potential and trigger electrode 15 which is at cathode potential. An arc discharge takes place between trigger electrodes 14 and 15 thus extending the ionized discharge path from trigger electrode 14 to cathode 30. This breakdown process continues very rapidly until the ionized discharge path extends from trigger electrode 12 to cathode 30.

It is a more diificult task to stretch this path all the way to the anode 20 because the voltage gradient is not as great since the anode 20 is already held at a high potential by capacitor 21. To ensure full and positive triggering of trigger electrode 11 and to make this trigger electrode the last to fire, I have employed breakdown device 25 intermediate the secondary winding 27 and trigger electrode 11. The trigger pulse from the secondary winding 27 is applied to electrode 23 of breakdown device 25 at substantially the same instant of time it is applied to the ends of trigger electrodes 12, 13, 14 and 15. Breakdown device 25 prevents the trigger pulse from reaching the probe end of trigger electrode 11 until the potential of the trigger pulse rises above a predetermined minimum voltage. By so doing, energization of trigger probe 11 is delayed, thus ensuring that it is the last trigger electrode to fire. Furthermore, a large amount of energy, essentially all that is remaining in the trigger transformer 26, is discharged through trigger electrode 11 into the weaker trigger spark that has already been formed from trigger electrode 12 to cathode 30. This greater trigger arc causes heavy ionization in the vicinity of the space between trigger electrode 12 and anode 20, thereby extending the ionized discharge path from cathode 30 to anode 20. Capacitor 21 then discharges its stored energy between principal electrodes 20 and 30 along this ionized discharge path. The heavy ionization caused by the increased energy applied to trigger electrode 11 shortens the commutation delay time, thereby increasing the speed of response of the device to triggering impulses. This also reduces jitter and increases the maximum repetition rate at which the discharge device 10 may be operated.

As an example, consider capacitor 21 to be a 0.5 ,uf. capacitor charged to about 600 volts and the trigger pulses to be short-duration 3000-volt pulses. When such pulses are fed to trigger electrodes 12, 13, 14 and 15, they fire on the leading edge of the pulses at about 1500 volts. The critical voltage of breakdown device 25 can be predetermined to insure that it does not fire until the trigger pulse voltage rises to about 2500 volts. In this way, trigger electrode 11 is made to fire last with greater energy than the other trigger electrodes. Although the breakdown device 25 introduces an infinitesimally small delay to the trigger pulse applied to trigger electrode 11, this action, due to the increased energy thereof, actually shortens the delay time between triggering and firing. In the above example, this delay time was reduced by approximately 55% by use of the breakdown device.

Although I have described my invention with a certain degree of particularity, modifications will occur to those skilled in the art and all such are deemed to fall within the spirit and scope of my invention.

I claim:

1. An electric system comprising:

a discharge device having an anode, a cathode and a plurality of trigger electrodes disposed therebetween;

means for connecting the anode and cathode across a source of potential normally ineffective to cause a discharge therebetween;

means for connecting each of said plurality of trigger electrodes to a source of triggering impulses;

a breakdown device connected in series with said source of triggering impulses and the trigger electrode adjacent the anode electrode, said breakdown device having a breakdown voltage which is greater than the firing voltage of the other trigger electrodes and less than the maximum voltage of the triggering impulses; and

isolating impedances disposed in said connecting means between each of the other trigger electrodes and said source of triggering pulses.

2. An electric system comprising:

a gaseous discharge device having within its envelope, an anode, a cathode spaced from the anode and a plurality of trigger electrodes disposed in the space therebetween;

means for connecting the anode and cathode across a source of potential normally ineffective to cause a discharge therebetween;

means for connecting each of said plurality of trigger electrodes to a source of triggering impulses;

a breakdown device disposed outside the envelope and connected in series with the source of triggering impulses and the trigger electrode adjacent the anode, said breakdown device having a breakdown voltage which is greater than the firing voltage of the other trigger electrodes and less than the maximum voltage of the triggering impulses; and

isolating impedances disposed in the connecting means between each of the other trigger electrodes and said source of triggering pulses.

3. An electric system as claimed in claim 2 in which said breakdown device is a spark gap.

4. An electric system as claimed in claim 2 in which said breakdown device is a diode.

5. In an electric system for controlling the operation of a gaseous discharge device of the type in which a plurality of trigger electrodes are disposed between an anode and a cathode, said anode and cathode being connected across a source of potential and said trigger electrodes being connected to a source of triggering impulses, the improvement for reducing commutation delay time and jitter of a breakdown device connected in the circuit of the trigger electrode adjacent the anode, said breakdown device having a breakdown voltage greater than the firing voltage of the other trigger electrodes and less than the maximum trigger voltage.

References Cited by the Examiner UNITED STATES PATENTS 2,406,853 9/1946 Richardson et a1. 315352 X 2,797,368 6/1957 Holden 313-352 X 2,977,508 3/ 1961 Germeshausen 315241 3,141,983 7/1964 Ward 315241 X FOREIGN PATENTS 760,674 11/1956 Great Britain.

JAMES W. LAWRENCE, Primary Examiner. 0 C. R. CAMPBELL, Assistant Examiner. 

1. AN ELECTRIC SYSTEM COMPRISING: DISCHARGE DEVICE HAVING AN ANODE, A CATHODE AND A PLURALITY OF TRIGGER ELECTRODES DISPOSED THEREBETWEEN; MEANS FOR CONNECTING THE ANODE AND CATHODE ACROSS A SOURCE OF POTENTIAL NORMALLY INEFFECTIVE TO CAUSE A DISCHARGE THEREBETWEEN; MEANS FOR CONNECTING EACH OF SAID PLURALITY OF TRIGGER ELECTRODES TO A SOURCE OF TRIGGERING IMPULSES; A BREAKDOWN DEVICE CONNECTED IN SERIES WITH SAID SOURCE OF TRIGGERING IMPULSES AND THE TRIGGER ELEC- 